There are numerous structures known for monitoring the level of liquid in a vessel, such as a tank, vat or sump, and either providing outputs indicating the level or taking various actions in response to the level.
Many different level sensing technologies have been used or proposed for such structures. For example, some such systems are based on sensors responsive to changes of pressure indicative of changes of liquid level. Others rely on the use of electrical probes whose electrical properties change with changes in the liquid level. However, many popular systems rely upon sensing the vertical displacement of a float floating on top of the liquid in the vessel.
Float mechanisms have been used in a variety of ways. In a conventional arrangement, a single float rises to a predetermined level, at which point an electrical switch or contact of some type is closed, thus energizing an associated electrical circuit such as an alarm or a pump motor.
Many systems utilize multiple pump and motor pairs to ensure that should one pump fail, another pump will turn on and ensure that the liquid is removed from the vessel.
One such arrangement uses a single float mechanism and a plurality of switches to turn on and off a series of pumps or alarms based on the level of the water in the vessel. One such system is disclosed in U.S. Pat. No. 8,985,964. This patent discloses the use of multiple micro switches. Each micro switch has an activation arm which cooperates with a specifically designed cam mounted on a float rod. The cam shape ensures that the activation arms are either activated or deactivated at various water levels to either activate or deactivate a pump corresponding to each micro switch.
However, in the apparatus disclosed in U.S. Pat. No. 8,985,964, the float switch apparatus is not sealed within a sump pit. According to many building codes, sump pits must be completed sealed from the external atmosphere to prevent the leakage of radon gas and other gases throughout a household or building. Furthermore any electrical components of the float switch apparatus must be completely isolated from the sump or vessel atmosphere to meet a variety of electrical or safety specifications. These electrical chambers must be vapor proof and water proof. As such, the multiple switch float apparatus as discussed in U.S. Pat. No. 8,985,964 may be insufficient for many geographical areas with safety requirements pertaining to sealed sump pits and/or electrical components which are required to be isolated from the sump atmosphere.
Currently sump pumps address the problem of maintaining a sealed sump pit by using a combination of floats such as tethered, pressure sensitive, vertical, magnetic reed and the like to perform the multiple tasks of operating several pumps and alarms. The float configuration would require multiple single float switches which can be expensive, cumbersome or prone to failure due to the various components becoming entangled with each other in the limited space of the sump pit vessel.